This paper presents an enhanced time-delay controller (TDC) for the position control of an autonomous underwater vehicle (AUV) under disturbances. A conventional TDC performs well when the involved ...data acquisition rate is fast. However, in AUV control applications that use a Doppler velocity log (DVL) navigation system, we cannot keep the data acquisition rate sufficiently fast because a DVL sensor generally supplies data at a slow acquisition rate, which degrades the performance of the TDC. To overcome this problem, we propose an integral sliding-mode controller to be supplemented to the conventional TDC to improve the control precision even if the DVL navigation system is in operation. The proposed controller is computationally simple and robust to unmodeled dynamics and disturbances. We performed computer simulations and experiments with the Cyclops AUV to demonstrate the validity of the proposed controller.
We propose the use of a second-order sliding-mode controller (2-SMC) to stabilize an autonomous underwater vehicle (AUV) which is subject to modeling errors and often suffers from unknown ...environmental disturbances. The 2-SMC is effective in compensating for the uncertainties in the hydrodynamic and hydrostatic parameters of the vehicle and rejecting the unpredictable disturbance effects due to ocean waves, tides, and currents. The 2-SMC is comprised of an equivalent controller and a switching controller to suppress the parameter uncertainties and external disturbances, and its closed-loop system is exponentially stable in the presence of parameter uncertainties and unknown disturbances. We performed numerical simulations to validate the proposed control approach, and experimental tests using Cyclops AUV were conducted to demonstrate its practical feasibility. The proposed controller increased the accuracy of trajectory tracking for an AUV in the presence of uncertain hydrodynamics and unknown disturbances.
This study proposes a 3-D seafloor scanning method using sonar images obtained by an acoustic lens-based multibeam sonar (ALMS). ALMS is a forward-looking sonar and is generally used to implement ...real-time acoustic vision for autonomous underwater vehicles (AUVs). ALMS is originally not a 3-D sonar, and elevation information is eliminated when the 3-D world is mapped to the 2-D sonar image. The proposed method provides a unique analysis of sonar image geometry for extracting the missing elevation information. Different from conventional 3-D reconstruction methods, the proposed method can be continuously executed regardless of the existence of any remarkable features in the sonar image, which means that the proposed method can scan the seafloor during a full-time AUV operation. Once the 3-D seafloor data are obtained, the height of the seafloor can be used for the detection of suspected objects. Therefore, the proposed method enables long-range seafloor object detection, triggering succeeding processes involving the AUV approaching the detected object, and the start of a detailed investigation at a close range.
Transparent electrodes based on conventional indium–tin oxide (ITO) can hardly meet the requirements of future generations of stretchable electronic devices, including artificial skins, stretchable ...displays, sensors, and actuators, because they cannot retain high conductivity under substantial stretching and bending deformation. Here we suggest a new approach for fabricating highly stretchable and transparent electrodes with good stability in environments where they would be stretched repeatedly. We designed polyurethane–urea (PUU), a urethane-based polymer, to enhance the adhesion between Ag nanowires (AgNWs) and poly(dimethylsiloxane) (PDMS). The adhesion could be further improved when irradiated by intense pulsed light (IPL). After delicate optimization of the layered AgNW/PUU/PDMS structure, we fabricated a stretchable transparent electrode that could withstand 100 cycles of 50% stretching–releasing, with exceptionally high stability and reversibility. This newly developed electrode is therefore expected to be directly applicable to a wide range of high-performance, low-cost, stretchable electronic devices.
Three-dimensional reconstruction is a crucial technique for mapping and object-search tasks, but it is challenging in sonar imaging because of the nature of acoustics. In underwater sensing, many ...advanced studies have introduced approaches that have included feature-based methods and multiple imaging at different locations. However, most existing methods are prone to environmental conditions, and they are not adequate for continuous data acquisition on moving autonomous underwater vehicles (AUVs). This paper proposes a sensor fusion method for 3D reconstruction using acoustic sonar data with two sonar devices that provide complementary features. The forward-looking multibeam sonar (FLS) is an imaging sonar capable of short-range scanning with a high horizontal resolution, and the profiling sonar (PS) is capable of middle-range scanning with high reliability in vertical information. Using both sonars, which have different data acquisition planes and times, we propose a probabilistic sensor fusion method. First, we extract the region of interest from the background and develop a sonar measurement model. Thereafter, we utilize the likelihood field generated by the PS and estimate the elevation ambiguity using importance sampling. We also present the evaluation of our method in a ray-tracing-based sonar simulation environment and the generation of the pointclouds. The experimental results indicate that the proposed method can provide a better accuracy than that of the conventional method. Because of the improved accuracy of the generated pointclouds, this method can be expanded for pointcloud-based mapping and classification methods.
Objectives This study sought to investigate the predictors and outcomes of side branch (SB) occlusion after main vessel (MV) stenting in coronary bifurcation lesions. Background SB occlusion is a ...serious complication that occurs during percutaneous coronary intervention (PCI) for bifurcation lesions. Methods Consecutive patients undergoing PCI using drug-eluting stents for bifurcation lesions with SB ≥2.3 mm were enrolled. We selected patients treated with the 1-stent technique or MV stenting first strategy. SB occlusion after MV stenting was defined as Thrombolysis in Myocardial Infarction flow grade <3. Results SB occlusion occurred in 187 (8.4%) of 2,227 bifurcation lesions. In multivariate analysis, independent predictors of SB occlusion were pre-procedural percent diameter stenosis of the SB ≥50% (odds ratio OR: 2.34; 95% confidence interval CI: 1.59 to 3.43; p < 0.001) and the proximal MV ≥50% (OR: 2.34; 95% CI: 1.57 to 3.50; p < 0.001), SB lesion length (OR: 1.03; 95% CI: 1.003 to 1.06; p = 0.03), and acute coronary syndrome (OR: 1.53; 95% CI: 1.06 to 2.19; p = 0.02). Of 187 occluded SBs, flow was restored spontaneously in 26 (13.9%) and by SB intervention in 103 (55.1%) but not in 58 (31.0%). Jailed wire in the SB was associated with flow recovery (74.8% vs. 57.8%, p = 0.02). Cardiac death or myocardial infarction occurred more frequently in patients with SB occlusion than in those without SB occlusion (adjusted hazard ratio: 2.34; 95% CI: 1.15 to 4.77; p = 0.02). Conclusions Angiographic findings of SB, proximal MV stenosis, and clinical presentation are predictive of SB occlusion after MV stenting. Occlusion of sizable SB is associated with adverse clinical outcomes. (Korean Coronary Bifurcation Stenting Registry II COBIS; NCT01642992 )
In this study, we propose an autonomous underwater vehicle (AUV)-based multi-directional scanning method of underwater objects using forward scan sonar (FSS). Recently, a method was developed that ...can generate a 3-D point cloud of an underwater object using FSS. However, the data comprised sparse and noisy characteristics that made it difficult for 3-D recognition. Another limitation was the absence of back and side surface information of an object. These limitations degraded the results of the 3-D reconstruction. We propose a multi-directional scanning strategy to improve the 3-D point cloud and reconstruction results where the AUV determines the direction of the next scan by analyzing the 3-D data of the object until the scanning is complete. This enables adaptive scanning based on the shape of the target object while reducing the amount of scanning time. Based on the scanning strategy, a polygonal approximation method for real-time 3-D reconstruction is developed to process scanned data groups of the 3-D point cloud. This process can efficiently handle multiple 3-D point cloud data for real-time operation and reduce its uncertainty. To verify the performance of our proposed method, simulations were performed with various objects and conditions. In addition, experiments were conducted in an indoor water tank, and the results were compared with the simulation results. Field experiments were conducted to verify the proposed method for more diverse environments and objects.
This paper proposes a method that synthesizes realistic sonar images using a Generative Adversarial Network (GAN). A ray-tracing-based sonar simulator first calculates semantic information of a ...viewed scene, and the GAN-based style transfer algorithm then generates realistic sonar images from the simulated images. We evaluated the method by measuring the similarity between the generated realistic images and real sonar images for several objects. We applied the proposed method to deep learning-based object detection, which is necessary to automate underwater tasks such as shipwreck investigation, mine removal, and landmark-based navigation. The detection results showed that the proposed method could generate images realistic enough to be used as training images of target objects. The proposed method can synthesize realistic training images of various angles and circumstances without sea trials, making the object detection straightforward and robust. The proposed method of generating realistic sonar images can be applied to other sonar-image-based algorithms as well as to object detection.
This study, utilizing the claims data from the Health Insurance Review and Assessment Service of Korea, aimed to examine the 10-year (2010-2019) trends in various types of lumbar spine surgeries ...performed on patients diagnosed with lumbar herniated intervertebral disc (HIVD), and the current status of opioid prescriptions, as well as the duration of postoperative hospital stays based on the type of surgery performed.
This retrospective cross-sectional study examined patients with one or more national health insurance claims carrying a primary or secondary diagnosis of HIVD (ICD-10 codes: M511, M518, M519) over a 10-year period (2010-2019). From the patients undergoing lumbar spine surgery, we selected those who did not require reoperation within 30 days following the initial lumbar surgery. Our final study sample comprised patients who underwent only one type of surgery.
Among the patients diagnosed with HIVD and subsequently undergoing lumbar surgery between 2010 and 2019, a slight downward trend was observed in those undergoing open discectomy (OD); however, OD persistently accounted for the highest proportion over the 10 years. Percutaneous endoscopic lumbar discectomy (PELD) demonstrated a consistent upward trend from 2016 to 2018. When inspecting trends, we noted a consistent escalation over the decade in the postoperative opioid prescription rates of strong opioids (50.7% in 2010 to 77.8% in 2019) and tramadol (50.9% in 2010 to 76.8% in 2019). Analyzing these trends by surgery type, spinal fusion exhibited a slightly higher rate of opioid prescriptions than other lumbar surgeries. Regarding the length of postoperative hospital stays, patients undergoing PELD recorded the shortest stay (7.04 ± 6.78 days), while spinal fusion necessitated the longest (20.14 ± 12.18 days).
This study analyzed the trends in types of lumbar spine surgeries, opioid analgesic prescriptions, and length of hospital stays over 10 years (2010-2019) among patients with HIVD in Korea. Our data and findings provide valuable evidence that may prove beneficial for clinicians and researchers involved in HIVD-related practices.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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